1. Field of the Invention
The present invention relates to a jig for producing a pellicle for use in photolithography, which pellicle is used as dust-proof protection of light-exposure originals having patterns in photolithographic patterning work in the production of semiconductor devices such as LSIs and VLSIs, liquid-crystal display devices and the like, and a method for producing a pellicle using the jig.
2. Description of the Related Art
In the fabrication of semiconductor devices, such as LSIs and VLSIs, and liquid-crystal display devices, a process comprising placing a light-exposure original (this term is herein used to collectively refer to photomasks, reticles and the like), and light-exposing the light-exposure original to transfer a pattern by the light transmitted through the original, i.e., photolithography, has been utilized.
However, if the light-exposure original used in such a process carries dust particles deposited thereon, the light beam is unevenly absorbed or scattered by the dust particles so that the pattern transferred on a semiconductor wafer, liquid crystal device substrate and the like may be deformed, the edge lines of a patterned area may be rugged without smoothness, or a white portion may be stained black. Thus, dimension, quality, appearance and the like of the pattern are disadvantageously degraded, and as a result, performance and production yield of semiconductor devices, liquid crystal display devices and the like may be degraded.
To obviate such a problem, the photolithography process is usually performed in a clean room. However, it is difficult to keep the light-exposure original in a perfectly dust-free condition even in a clean room. Therefore, to prevent the adhesion of dust particles and the like onto the light-exposure original surface, a transparent pellicle sufficiently transmitting the light for the light exposure is applied on the original.
When a pellicle is applied, dust particles are not adhered directly on the light-exposure original surface but on the pellicle membrane. Therefore, if the light is focused on the pattern of the light-exposure original during the photolithography process, the presence of such dust particles does not influence on the pattern transfer, and thus the aforementioned problem is not caused.
The aforementioned pellicle is produced by spreading a pellicle membrane on a pellicle frame, and the outline of the production method therefor is as follows.
First, a pellicle membrane is formed by solution casting or the like on a substrate composed of silicon single crystal, synthetic quartz or the like using a material sufficiently transmitting light, for example, cellulose nitrate, cellulose acetate, fluorocarbon resin, and the like.
Then, a jig for producing a pellicle comprising a support frame having an opening at its center, and an adhesive layer provided around the opening is used to adhere the pellicle membrane on the adhesive layer, and separate the jig from the substrate. As a result, the pellicle membrane is peeled off from the substrate and held on the adhesive layer of the jig for producing a pellicle.
Thereafter, a pellicle frame is adhered to this pellicle membrane, and a pellicle is produced by trimming the pellicle membrane along the outer periphery of the pellicle frame.
The adhesive layer of the jig for producing a pellicle used for the above production process is usually composed of a double-sided adhesive tape, or prepared from an adhesive such as acrylic resin and epoxy resin.
However, when a double-sided adhesive tape or an adhesive such as acrylic resin and epoxy resin is used as the aforementioned adhesive layer as mentioned above, an unnecessary pellicle membrane remains on the adhesive layer after a pellicle is once produced, and therefore the adhesion of the surface of adhesive layer is lost. Accordingly, it cannot be used as the adhesive layer again as it is. Therefore, in order to use this jig for producing a pellicle again, it is necessary to remove the adhesive layer after use, and form another adhesive layer again. However, such formation of adhesive layer is not preferred in view of production efficiency since it takes time, and it also suffers from the problem of increase of the cost for the adhesive layer.
Therefore, jigs for producing a pellicle have sometimes been disposed after they were used once. Although such a method may in fact save time and labor, it still disadvantageously suffers from the problem concerning the production cost.
The present invention has been accomplished in view of the aforementioned problems, and its major object is to provide a jig for producing a pellicle which can be repeatedly used without reforming the adhesive layer after use, and a method for producing a pellicle using it. In order to achieve the aforementioned object, the present invention provides a jig for producing a pellicle comprising a support frame having an opening, and an adhesive layer provided at periphery of the opening, characterized in that the adhesive layer is composed of a polymer material having a glass transition temperature within a range of 0xc2x0 C. to 300xc2x0 C.
The adhesive layer composed of a polymer material having a glass transition temperature within a range of 0xc2x0 C. to 300xc2x0 C. can be adhered to the pellicle membrane when it is softened or melted by heating to a temperature higher than its glass transition temperature, and contacted with a pellicle membrane. Further, though the adhesive layer would have an unnecessary pellicle membrane thereon after once producing a pellicle, the adhesive layer having the unnecessary pellicle membrane can be adhered again to another new pellicle membrane when it is softened or melted again as it is by heating, and contacted with the new pellicle membrane. This makes it possible to repeatedly use the jig without reproducing the adhesive layer, and thus reduction of time and cost required for the production of pellicle can be realized.
In the jig of the present invention, the polymer material used for the adhesive layer is selected so that a value obtained by subtracting a glass transition temperature of the polymer material of the adhesive layer from a glass transition temperature of a polymer material of the pellicle membrane used for the pellicle to be produced should be less than 60xc2x0 C.
When the value obtained by subtracting a glass transition temperature of the polymer material of the adhesive layer from a glass transition temperature of polymer material for the pellicle membrane is 60xc2x0 C. or more, the glass transition temperature of the adhesive layer substantially approaches room temperature, and hence its handling becomes difficult. Moreover, in such a case, when the pellicle membrane is heated to a temperature more than its glass transition temperature, the rigidity of the adhesive layer is reduced, and hence it may be likely that wrinkles are generated in the pellicle membrane due to decrease of its tension when it is peeled off from the substrate and transferred to the adhesive layer. For these reasons, the above mentioned value is defined.
Further, in the jig of the present invention, it is desirable that the polymer material of the adhesive layer should be a polymer material having compatibility with the polymer material of the pellicle membrane.
This is because the polymer material of the adhesive layer and the polymer material of the pellicle membrane exhibiting compatibility with each other can be easily adhered when they are heated and contacted with each other, and the adhesion strength obtained by the thermal adhesion also becomes higher.
In such a case, it is preferred that the polymer material of the adhesive layer should be the same material as the polymer material of the pellicle membrane.
The use of the same materials is advantageous in view of the adhesion because the adhesive layer and the pellicle membrane can be softened and melted by simultaneous heating. In addition, it is also advantageous in view of the repetitive use of the adhesive layer, because the adhesive layer surface can be the same material as the original material after the repetitive use, and hence the condition for adhesion can be constant.
Further, in the jig of the present invention, it is desirable that the polymer material of the adhesive layer should be a fluorocarbon resin.
In recent years, use of light having a wavelength of 248 nm of krypton fluoride excimer laser and light having a wavelength of 193 nm of argon fluoride excimer laser in the light exposure process of the semiconductor production becomes popular, and fluorocarbon resins well transmitting these lights are often used as a material of pellicle membrane. However, fluorocarbon resins do not show good adhesion with other kinds of resins. Therefore, when the material of the pellicle membrane is a fluorocarbon resin, it is desirable that the material of the adhesive layer should also be a fluorocarbon resin.
The present invention also provides a method for producing a pellicle, characterized in that it comprises the steps of forming a pellicle membrane; adhering the formed pellicle membrane to the adhesive layer of the aforementioned jig for producing a pellicle according to the present invention by heating the pellicle membrane and/or the adhesive layer to a temperature more than their glass transition temperatures and contacting them with each other, so that the pellicle membrane should be held on the adhesive layer; adhering a pellicle frame on the pellicle membrane held on the adhesive layer; and trimming the pellicle membrane along outer periphery of the pellicle frame.
By producing pellicles using the aforementioned jig for producing a pellicle, the production efficiency can be improved because the jig for producing a pellicle can be repeatedly used.
The jig for producing a pellicle of the present invention comprises a support frame having an opening, and an adhesive layer provided at periphery of the opening, and is characterized in that the adhesive layer is composed of a polymer material having a glass transition temperature within a range of 0xc2x0 C. to 300xc2x0 C. Therefore, the adhesive layer can be softened or melted by heating it to a temperature higher than its glass transition temperature, and brought into contact with a pellicle membrane to achieve adhesion with the pellicle membrane. Further, though the adhesive layer would have an unnecessary pellicle membrane thereon after once producing a pellicle, it can be adhered again to another new pellicle membrane for producing another pellicle when it is softened or melted again as it is by heating and contacted with the new pellicle membrane. This makes it possible to repeatedly produce pellicles without reproducing the adhesive layer of the jig, and thus reduction of time and cost required for the production of pellicle can be realized.